As per the symptoms yes it looks like
muscular pain only. I suggest to use hot pack on your back. This will help to relax the softtissue at back. As well also apply pain relieving ointment for some more relief. Here since you have complain of pain mainly when you wake up in morning looks like associated with muscle catch so I suggest you should also take
muscle relaxant tablet for one or two days. You can also take pain killer if needed.
In case if you have pain from your back to legs radiating along with
numbness then there could be possibility of problem with your lumbosacral spine, disc, or nerves coming from this levels.
For this I suggest to take
MRI of back and check with orthopedic doctor. Here based on report he will suggest surgical correction in case there is major damage at spine,disc level. In case its normal or mild to moderate issue then he will ask you to take
physiotherapy.
For all above cases I suggest to visit physio for postural correction, spinal exercises suggestion and if needed treatment. This will help to reduce inflammation, pain, and will help to improve strength and stamina of your spine.
Take care.